Love and sex are always complicated issues. I will give you a straight answer to your question but I would also like to address what seem to me to be the underlying issues behind your question. Also, how I discuss the topic differs depending on whether I am talking to an adult, with all of an adult’s life-experiences, or a teenager. Although I suspect the latter, I will try to answer in two ways so as to be relevant to your age and life-experience, which I do not actually know.
On the simplest level, according to strict halakha, if a woman has relations with a non-Jewish man, she is definitely still eligible to marry a Jewish man. There is no taint. However, she may not marry a kohen, but this rule is generally only enforced in the Orthodox community. Lack of virginity itself, in some communities, may affect the wording of a ketubah (the document has the word virgin in it) but many communities, even Orthodox ones, often leave the word in any way for first marriages.
Insofar as sex with a Gentile man goes, halakha does not permit this at all, nor does it look favorably on pre-marital sex in general – but you did not ask me this, and it is a decision you will have to make on your own.
That said, let me share with you my concerns about your question, not from the perspective of Jewish law but from a pastoral perspective. You are saying that you love this man deeply enough that you are planning on losing your virginity with him but you seem to have – or believe you have – no intention of marrying him. Personally, I find this sentiment somewhat worrisome. The reasons for this differ significantly depending on your age, so here I will explain twice.
If I am speaking with a teenager (or even a very young adult), I have a number of concerns. Although I am well aware of the fact that teenagers having sex has become more common in recent years, this often comes with negative consequences. I am not referring here to pregnancy or STDs, although I will assume here (I hope not naively) that you are aware of these risks and how to prevent them. What I am referring to is the emotional risk. Although in a committed relationship sex can build up a person’s self-esteem and self-love, in a non-committed relationship it can have the opposite effect, especially on young girls.
I fear that in our promiscuous society, many girls (and women) suffer from body image doubt and low self-esteem and mistakenly believe that making boys/men “happy”—at whatever cost—will help with this. In my estimation, however, it generally has the opposite effect. Sex is a very personal and intimate activity, and girls may feel degraded having exposed themselves in this way to a boy who then moves on to someone else. Boys (and men) have the unfortunate tendency to commoditize girls (and women)—the proverbial notch on the belt—and you do not want to expose yourself to this. (I recommend Wendy Shalit’s books A Return to Modesty and Girls Gone Mild if you want to give this more thought.)
Of course, you write that you love him and I hope that this means you are in a committed relationship with him. And yet, you are not even thinking of long term with him, which I assume is because you are too young to think of marriage. But you still do not think you are too young to think of sex or to know when love is commitment or love is a short term burst of feeling that will fizzle out. In short, I worry you are more confused than you know or let on, and would caution you to be careful. If you are planning on sex at a tender age—and I do not advocate for this—listen to your gut and never do anything that the back of your mind says you will regret… your subconscious knows what it is talking about. Also, just to be safe, please never make any important decisions while intoxicated or under pressure.
If I am speaking to an adult, especially one who has dated for a while and not found someone, this must be a confusing time for you. Finally, you found someone you love and you are planning on starting to be intimate with—the type of relationship many of your friends probably already take for granted—and he is not Jewish. Here is my question for you: how are you so sure you will not marry him? You love him, you will be sleeping with him and you are both adults – this is exactly what leads to marriage.
Is the only reason you do not think you will marry him because he is not Jewish? If that is it, I believe—if the relationship is a good one—you will soon find yourself wanting to marry him. I suggest you start thinking about how important it is for you to marry a Jew. If this is very important to you, I suggest you either break off the relationship before doing so would be impossible or speaking frankly with him about whether he would be willing to convert. If he would not be, would he be willing to assist you in bringing up the children Jewish, join a synagogue, etc.? On the other hand, if you feel that discussing marriage with him would be premature, or that he would never consider it, maybe sleeping with him is premature as well.
Either way, whether you are a teenager or an adult, keep this in the back of your mind: even if you make the wrong decision here, don’t be too hard on yourself, relationships are tricky things. Just try—as you are doing—not to lose sight of your ultimate goal to marry Jewish and start a Jewish family.